Research Specifications

Despite extensive research on the elastic local buckling, post-buckling resistance, and geometric imperfections of coped beams at ambient temperatures, their behavior under fire and post-fire conditions has remained almost entirely unexplored. This paper presents the first comprehensive investigation into the structural response of coped steel I-beams with thin web panels (CBTWs) exposed to elevated-temperature and post-fire conditions. A comprehensive set of high-fidelity finite element analyses was performed to systematically investigate the effects of key geometric parameters—namely, the ratios of cope depth to beam depth (dc/D), cope length to beam depth (Lc/D), web slenderness (h/tw), and flange-to-web stiffness ratio (tf/tw). The results demonstrated that at room temperature, smaller cope regions promote brittle failure, whereas slender webs provide improved post-buckling resistance. Under fire exposure, the ultimate strength progressively decreases with temperature, while rapid water cooling partially restores residual strength. Moreover, Fire-damaged CBTWs with shear slenderness parameter λs < 2.5 primarily fail through inelastic local buckling, whereas beams with λs > 2.5 exhibit elastic local buckling followed by post-buckling, establishing λs = 2.5 as a critical threshold for failure classification. Building on these insights, new design equations and predictive curves were proposed to estimate residual and ultimate resistance, failure time, limiting temperature, and governing mechanism of CBTWs. These findings not only extend current design methodologies to include fire and post-fire effects but also provide engineers with reliable tools for making informed decisions in designing fire-resilient structural systems.